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Mon, 4 May 2026 08:25:32 +0000 (GMT) From: Sayali Patil To: Andrew Morton , Shuah Khan , linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org, Ritesh Harjani Cc: David Hildenbrand , Zi Yan , Michal Hocko , Oscar Salvador , Lorenzo Stoakes , Dev Jain , Liam.Howlett@oracle.com, linuxppc-dev@lists.ozlabs.org, Miaohe Lin , Venkat Rao Bagalkote , Sayali Patil Subject: [PATCH v6 09/14] selftest/mm: register existing mapping with userfaultfd in hugepage-mremap Date: Mon, 4 May 2026 13:54:46 +0530 Message-ID: X-Mailer: git-send-email 2.52.0 In-Reply-To: References: Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-TM-AS-GCONF: 00 X-Proofpoint-Reinject: loops=2 maxloops=12 X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwNTA0MDA4NyBTYWx0ZWRfX3QI6zhoFeIPq Jhy3gEWfDVdNkdSQUQzVq7BcVcFRIJQ7lh8FTHqmQHoUcnRZw1dyO/46epImoRqwPemPFcdaVg2 dL4lFQsGp8cL2gA7ZZfD7s9mLhe9l7dTRVVC4SBuK12TMK0Lra8faFC0N1Ln3X+3e5d/RW6G7JV 87RYalSH1dAL0eYjOa5K7mFya4sACGZNkK2eXCvWtaKJ57f4gUfv1Txrh9dCkDIqm+V61nljp1y /+hrTQvZGx7e4BiiI5JGDAzATVwQlFeR7vzID3xZmFWMf/w0I9LaFSv0Wg5XUIYErBRflyqWJ8T YhDxaKCE5RTTr1QxdnXKKhJOol9eNIK2x0+En4oyT80B0SC+9bICMGTa/WKALzfspDVJ7xevssi mLIS/u6axU/yDY2pgZYkycnTbwhUSlWWFVwq/Zuc8jBO4NsvH5vJXkz3RkST6yyCNvVy6ZlPCjh vfD7RDTEEjCXTYfe/0g== X-Proofpoint-ORIG-GUID: uPn6RHkmEbhPoeqYvp2cKeh83IV8X9Y5 X-Proofpoint-GUID: wfQhWfwlxQb2Uk9D0i_52QNHqRi6jSjT X-Authority-Analysis: v=2.4 cv=W7UIkxWk c=1 sm=1 tr=0 ts=69f85805 cx=c_pps a=5BHTudwdYE3Te8bg5FgnPg==:117 a=5BHTudwdYE3Te8bg5FgnPg==:17 a=NGcC8JguVDcA:10 a=VkNPw1HP01LnGYTKEx00:22 a=RnoormkPH1_aCDwRdu11:22 a=uAbxVGIbfxUO_5tXvNgY:22 a=VwQbUJbxAAAA:8 a=VnNF1IyMAAAA:8 a=gVE5Qc0x_BWLnb-D2gsA:9 X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1143,Hydra:6.1.51,FMLib:17.12.100.49 definitions=2026-05-04_03,2026-04-30_02,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 priorityscore=1501 adultscore=0 lowpriorityscore=0 malwarescore=0 suspectscore=0 spamscore=0 clxscore=1015 phishscore=0 bulkscore=0 impostorscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2604200000 definitions=main-2605040087 Previously, register_region_with_uffd() created a new anonymous mapping and overwrote the address supplied by the caller before registering the range with userfaultfd. As a result, userfaultfd was applied to an unrelated anonymous mapping instead of the hugetlb region used by the test. Remove the extra mmap() and register the caller-provided address range directly using UFFDIO_REGISTER_MODE_MISSING, so that faults are generated for the hugetlb mapping used by the test. This ensures userfaultfd operates on the actual hugetlb test region and validates the expected fault handling. Before patch: running ./hugepage-mremap ------------------------- TAP version 13 1..1 Map haddr: Returned address is 0x7eaa40000000 Map daddr: Returned address is 0x7daa40000000 Map vaddr: Returned address is 0x7faa40000000 Address returned by mmap() = 0x7fff9d000000 Mremap: Returned address is 0x7faa40000000 First hex is 0 First hex is 3020100 ok 1 Read same data Totals: pass:1 fail:0 xfail:0 xpass:0 skip:0 error:0 [PASS] ok 1 hugepage-mremap After patch: running ./hugepage-mremap ------------------------- TAP version 13 1..1 Map haddr: Returned address is 0x7eaa40000000 Map daddr: Returned address is 0x7daa40000000 Map vaddr: Returned address is 0x7faa40000000 Registered memory at address 0x7eaa40000000 with userfaultfd Mremap: Returned address is 0x7faa40000000 First hex is 0 First hex is 3020100 ok 1 Read same data Totals: pass:1 fail:0 xfail:0 xpass:0 skip:0 error:0 [PASS] ok 1 hugepage-mremap Fixes: 12b613206474 ("mm, hugepages: add hugetlb vma mremap() test") Acked-by: David Hildenbrand (Arm) Tested-by: Venkat Rao Bagalkote Signed-off-by: Sayali Patil --- tools/testing/selftests/mm/hugepage-mremap.c | 21 +++++--------------- 1 file changed, 5 insertions(+), 16 deletions(-) diff --git a/tools/testing/selftests/mm/hugepage-mremap.c b/tools/testing/selftests/mm/hugepage-mremap.c index f66e4d806477..68c35d1d8a5f 100644 --- a/tools/testing/selftests/mm/hugepage-mremap.c +++ b/tools/testing/selftests/mm/hugepage-mremap.c @@ -86,25 +86,14 @@ static void register_region_with_uffd(char *addr, size_t len) if (ioctl(uffd, UFFDIO_API, &uffdio_api) == -1) ksft_exit_fail_msg("ioctl-UFFDIO_API: %s\n", strerror(errno)); - /* Create a private anonymous mapping. The memory will be - * demand-zero paged--that is, not yet allocated. When we - * actually touch the memory, it will be allocated via - * the userfaultfd. - */ - - addr = mmap(NULL, len, PROT_READ | PROT_WRITE, - MAP_PRIVATE | MAP_ANONYMOUS, -1, 0); - if (addr == MAP_FAILED) - ksft_exit_fail_msg("mmap: %s\n", strerror(errno)); - - ksft_print_msg("Address returned by mmap() = %p\n", addr); - - /* Register the memory range of the mapping we just created for - * handling by the userfaultfd object. In mode, we request to track - * missing pages (i.e., pages that have not yet been faulted in). + /* Register the passed memory range for handling by the userfaultfd object. + * In mode, we request to track missing pages + * (i.e., pages that have not yet been faulted in). */ if (uffd_register(uffd, addr, len, true, false, false)) ksft_exit_fail_msg("ioctl-UFFDIO_REGISTER: %s\n", strerror(errno)); + + ksft_print_msg("Registered memory at address %p with userfaultfd\n", addr); } int main(int argc, char *argv[]) -- 2.52.0